Unknown filter action forward

[Jerome]

Ever since upgrading to Kmail 5.22.0, every time I start KDE I get an 
Information dialog from the Mail Filter Agent

    Unknown filter action forward in filter rule XXXX

Except I don't have such an action in my filter rules.

This also happens with the latest Fedora 38.

Googling finds nothing useful for "Unknown filter action" KMail.

It only happens when KDE starts so it's an annoyance, but... any ideas?